Lamp



March 24, 1936. G. SPERTI 2,034,998

LAMP

Filed Jan. 15, 1932 2 Sheets-Sheet 1.

G. SPERTI March 24, 1936.

LAMP

Filed Jan. 15, 1932 2 Sheets-Sheet 2 i lllllfilf-wlllllillil nllurllllln llwiliillllilll is! I Patented Mar. 24, 1936 .UNl'lED- STATE E N F El George Sperti, Covington, Ky., assignor to Spo Lamp Corporation, New York, N. Y., a corporation of Delaware This invention relates to electric lamps of the type combining an incandescent filament as a source of visible radiation and an arc constituting a source of visible and ultraviolet radiation.

In my prior application for United States Letters Patent, Serial No. 510,412, filed January 22, 1931, there is disclosed a lamp comprising a bulb in which are positioned a pair of spaced electrodes for establishing and maintaining an arc, and an inner bulb in which is an incandescent filament, the filament and arc electrodes being suitably connected across the terminals of the lamp so as to constitute a unitary light source which may be screwed into the ordinary light socket. In my prior application for United States Letters Patent, Serial No. 572,394, filed October 31, 1931, there is disclosed a lamp wherein the incandescent filament is located in the outer bulb and the arc electrodes are positioned in an inner bulb. The separate enclosure of the arc and of the incandescent filament in either case permits the operation of these two sources substantially independently as regards conditions such as vapor or gas pressure and prevents the arc striking to the filament. The circuits in these lamps each comprise an incandescent filament which is in series with the are between the two electrodes and an incandescent filament or filaments in parallel with the arc electrodes, the latter filament or filaments including means for heating the electrodes for starting and maintaining the arc. Either or both of these filaments may constitute sources of visible radiation, and the series filaments acts as a ballast for the arc current.

When current is first supplied to a lamp of this kind, there is a short period before the arc strikes during which the series filament and parallel filament constitute an ordinary series circuit through the lamp, but as soon as the arc strikes, the resistance in the are path tends to decrease to a low value and hence the current through the parallel filament tends to decrease. The voltage across the arc drops simultaneously and the current through the series filament tends to increase. Where the parallel filament is relied on as a source of visible radiation, it is necessary to provide means in series with the arc to limit the arc current after the arc strikes in order to maintain the parallel filament at incandescence. Where the series filament is relied on as a source of visible radiation and the parallel filament is employed principally for heating the arc electrodes during starting, it is necessary to proportion the series filament so that it will carry the 'total current through the lamp during normal operation and will operate at high lighting em- 'ciency and high temperature. During the initial period before the arc strikes, however, the current through the series filament is less than the current during normal operation and hence the tendency is for this series filament to burn only dimly until after the arc strikes. If the series filament is proportioned to burn brightly before the arc strikes, it tends to burn out when the current increases due to the decrease of the resistance of the arc path. On the other hand, if additional ballast resistance is placed in series with this filament so as to limit the arc current, the effect is to decrease the voltage across the parallel filament and hence to decrease the voltage which is available for causing the arc to strike, and also to decrease the lighting efiiciency of the incandescent filament.

One object, of this inventionis to provide a lamp of the class described wherein the incandescent filament may be operated at high lighting efiiciency both before and after the arc strikes without danger of burning out the filament.

Another object is to provide a lamp of the type described with novel means for controlling and limiting the arc current without in any way affecting the operation of the lamp for are starting purposes.

Several embodiments of the invention have been illustrated in the accompanying drawings, but it is to be expressly understood that said drawings are for purposes of illustration only and are not to be construed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings,

Fig. 1 is a perspective view of a lamp embodying the invention;

Fig. 2 is a sectional view of a portion of another lamp embodying the invention;

Fig. 3 is a sectional view of a portion of a still further form of lamp embodying the invention;

Fig. 4 is a sectional view of a portion of another lamp embodying the invention; and

Figs. 5 to 8, inclusive, are respectively wiring diagrams of the lamps shown in Figs. 1 to 4 inclusive.

Fig. 1 shows a lamp of the same general type as that disclosed in the aforesaid application for patent, No. 572,394. This lamp comprises an 50 outer bulb I of any suitable type, size and shape which is supported by the usual or any suitable base 2. Within the neck of the bulb i is sealed a stem or standard 3 which constitutes the usual means for introducing conductors 4 and 5 into 55 radiation from the filament and the arc.

the bulb and for supporting the various elements within the bulb. An incandescent filament 6, preferably of tungsten, is supported within the bulb I by means of supporting wires I and 3 which are fused in the stem 3, the wire I constituting a connection between the conductor 4 and one end of the filament 6. Said filament may also be supported by one or more wires 9 secured to a bead I 0 formed on the upper end of an inner bulb I I which is mounted in the lamp by means of a supporting band I2 and supports I3 and I4 that are fused in the stem 3. The inner bulb II encloses a pair of electrodes I5 and I6 of any suitable type, said electrodes being mounted in the inner bulb by supports I I and I 8.

The incandescent filament 6 in the outer bulb constitutes a source of visible radiation, and the arc electrodes I5, I6 establish an arc in the inner bulb II in an atmosphere of mercury vapor or other suitable gas or vapor, the resultant spectrum of the lamp being a combination of the Preferably the outer bulb I is of suitable material which transmits ultra-violet light, and the inner bulb II is of material which transmits ultraviolet light of wave lengths longer than a predetermined limit, preferably in the neighborhood of 2600 to 2900 Angstrom units. The light from such a lamp closely resembles natural sunlight in character and quality both as regards the visible part of the spectrum and as regards the invisible ultra-violet part of the spectrum. It will be understood, however, that the construction of the lamp as thus far described constitutes no part per se of the present invention but is shown merely for purposes of illustrating the application of the invention to a practical form of lamp.

The filament 6 constitutes the series filament referred to above which in this case is relied on principally as a source of visible radiation, the parallel filaments being employed primarily for the purpose of heating the electrodes I5 and I6. As pointed out above, one end of the filament 6 is connected to the conductor 4, and as shown in Fig. 1 the other end of said filament is connected by a wire I9 with a heating filament 20 disposed within the electrode I6, said heating filament being connected by a wire 2| with a second heating filament 22 positioned within the electrode I5. Wire2 I may if desired include a resistance 23. The other end of the heating filament 22 is connected by a wire 24 with the support I3 and the support I3 is connected with the conductor 5. The heating filaments 20 and 22, and the resistance 23 if employed, constitute a circuit in parallel with the arc electrodes I5, I6 and the potential drop through this circuit is applied across the electrodes for establishing and maintaining the arc. To this end the wire I9 is connected to the support I8 of the electrode I6 and the wire 24 is connected with the support I! of the electrode I5, these connections including resistances 25 and 26, the function of which will be described hereinafter.

The operation of the lamp circuit will be described with reference to Fig. 5. When current is first supplied to the lamp, it passes in series through the filament 6, heating filament 20, resistance 23, and heating filament 22. The filament 6 immediately heats up to incandesence, and the heating filaments 20 and 22 heat the electrodes I5 and I6. During the period before the arc strikes, the filaments 6, 20 and 22 and the resistance 23 constitute a series circuit connected across the conductors 4 and 5. a considerable part of the voltage drop being in the circuit in parallel with the electrodes which includes the heating filaments 20 and 22 and the resistance 23. This parallel circuit is proportioned to provide the proper amount of heat for the electrodes and also to provide the desired voltage across the electrodes for starting the arc, the resistance 23 being employed if necessary. As soon as the arc strikes, the resistance of the arc path between the electrodes I5 and I5 is greatly decreased and most of the current flows through the arc, the current through the parallel heating filament circuit being greatly decreased and the voltage drop thereacross being also decreased. The tendency therefore is for the current through the series filament 6 to increase.

Heretofore it has been necessary to proportion the filament 6 so that its lighting efficiency is high on the increased current after the arc strikes and hence said filamenthas not operated efficiently during the short period before the arc strikes. At the same time it has not been practicable to insert additional resistance in series with the filament 6 because such resistance would have decreased the voltage drop through the parallel heating circuit and hence would have decreased the starting voltage applied to the arc, and also would have decreased the lighting efiiciency of the filament 6. In accordance with the present invention, the resistances 25 and 26 are employed to limit the arc current. During the period before the arc strikes, no current fiows through these resistances since they are in the leads to the electrodes I5 and I6 and hence said resistances do not affect in any way the operation of the circuit for heating the electrodes and starting the arc. After the arc strikes, the resistances 25 and 26 act to limit the current through the arc and hence to prevent or limit an increase of current through the filament 6. Accordingly, the filament 6 may be proportioned to have high lighting efiiciency both during the initial starting period and during normal operation of the lamp. At the same time the characteristics of the circuit which are desired for starting the arc are not affected.

Fig. 2 shows another form of lamp wherein the arc electrodes are placed side by side instead of end to end as in Fig. 1. In Fig. 2, the bulb 21, base 28 and stem or standard 29 may be as described in connection with Fig. 1. The lamp is provided with the usual conductors 30 and 3I which are sealed in the lamp base, and the stem 29 carries supporting wires 32 and 33 for an incandescent filament 34, the latter being also supported by wires 35 secured to the inner bulb 36. A supporting band 31 and supports 38 and 39 serve to mount the bulb 36 on the stem 29, and a stem or standard 40 sealed in the neckof the inner bulb 36 serves to support a pair of electrodes 4| and 42 carried by supporting wires 43 and 44. Preferably the electrodes M, 42 have the form of tubes of suitable material such as nickel which are partially or entirely coated with one or more oxides of strontium, barium, thorium, etc., to aid in starting the arc. Said electrodes may also be protected by suitable grids or wire coils indicated at 45 and 46.

The lamp circuit of this lamp is shown more clearly in Fig. 6. The filament 34 is connected in series with heating filaments 41 and 48 positioned within the electrode tubes 4| and 42 as lamp shown in Figs. 1 and 5.

A still further form of lamp is illustrated in Figs. 3 and 7. As shown in Fig. 3, said lamp comprises a bulb 5|, base 52, stem 53, and conductors 54 and 55. An incandescent filament 56 is supportedin the bulb by means of wires 5'! and 58 fused in the stem 53 and also by means of wires 59 carried by the inner bulb 60 which is in turn supported on the stem 53 by means of a band 6| and supports 62 and 63. Within the inner bulb 60 is a single electrode element having the form described and claimed in theco-pending application of George Sperti, Serial No. 586,851, which issued May 1, 1934, as Patent No. 1,956,598. This element comprises a body 64 of insulating material such as magnesium oxide having electrode sleeves 65 and 66 secured on itsopposite ends. The electrode element is mounted in the inner bulb by means of a supporting band '67 and supports 68 and 69 and isprovided with a plurality of passages 10 through which the heating filaments and connecting wires pass.

The lamp circuit is shown more clearly in Fig. 7. The incandescent filament 56 is in series with heating filaments II and i2 which as shown in Fig. 3 are positioned in the outer passages 70 and serve to heat both of the electrode sleeves 65 and 66. The voltage drop through these heating filaments is applied to the electrodes, the electrode 66 being connected by a wire 13 with one end of the filament 56 and the electrode 65 being connected by a wire 74 and resistance 15 with the conductor 55. As shown in Fig. 3, resistance 15 is enclosed in the central passage 10. The operation of this circuit will be understood from the foregoing description of Figs. 5 and 6, the single resistance 75 being in series with the arc current and serving to limit the same in the same way as the resistances 25 and 26 of Figure 5.

Fig. 4 shows another form of lamp wherein the series filament is eliminated and the parallel filament is relied on both to heat the electrodes and to provide a source of visible radiation. This lamp comprises as shown an outer bulb 16, base ll, stem 18 and conductors i9 and 80. An incandescent filament 8| is mounted in the bulb in the usual manner, said filament being supported by wires 82 and 83 fused in the stem 18 and by wires 85 carried by the inner bulb 85 which is mounted on the stem 18 as described above. Within the inner bulb is a pair of electrodes 66 and 87 which as shown have the form of tubes closed at one end and supported by wires 88 and 86. These electrodes are heated by filaments 90 and Si.

Referring now to Fig. 8, the filament 8i and the heating filaments 90 and 9! are connected in series across the conductors i9 and 80 and constitute a circuit in parallel with the arc electrodes 86 and 81. When current is supplied to the lamp, these filaments heat up, filament 8i constituting an incandescent source and filaments 9B and 9! heating the electrodes 86 and 81. In this instance the entire voltage drop across the lamp is applied to the electrodes 86 and 81. As soon as the are strikes, current flows in parallel with the filament 8i by way of the wire 92, resistance 93, electrodes 86 and 87, resistance and wire 95. The arc current however, is limited by the resistances 33 and 94 to a suitable value and there is substantially no drop in the current flowing through the filament 6| so that the operation of said filament 8| as an incandescent source of visible radiation is not interfered with.

It will be seenthat the invention provides means whereby the incandescent filament may be operated at high lighting efiiciency both before and after the arc strikes without danger of burning out the filament due to the current-limiting efthe arc. At the'same time this result is accomplished without in any way affecting the characteristics of the arc circuit for purposes of starting the arc. Thus the circuit may be designed to provide the proper amount of heat for the electrodes and potential drop across the electrodes in that portion of the circuit which is in parallel with the electrodes and the incandescent filament may be proportioned to operate efliciently without regard to the change in conditions when the'arc strikes as explained above. The resistances in series with the arc may if desired be light-emitting filaments and to this ,end may be placed in any desired location within the lamp. For example, the resistances 25 and 26 of Fig. 1

may be so positioned as to emit visible radiations after the arc strikes and the same is true of the lamps shown in Figs. 2, 3 and 4. It will therefore be understood that the arrangement of the various elements within the lamp may be varied according to the effects which are desired. Also the arc electrodes may if desired be placed in the outer chamber and the incandescent filament or filaments may be placed in an inner chamber as disclosed in the aforesaid application, Serial No. 510,412. In either case the operation of the lamp is the same as respects the present invention. Moreover, as respects some features of the invention, it is not always necessary that the incandescent filament and the are be operated in separate chambers.

It will accordingly be understood that the invention is not restricted to the several embodiments thereof which have been described and illustrated in the drawings, but is capable of a variety of physical expressions. Moreover, changes may be made in the details of construction and arrangement of the parts without departing from the spirit of the invention. Thus the radiation which is to be produced, etc. Ref;

erence is therefore to be had to the appended claims for a definition of the limits of theinvention.

What is claimed is:

1. An electric lamp comprising a pair of terminals, a plurality of filaments in said lamp and connected in series across said terminals, a pair of arc electrodes connected to said series circuit at points of different potential, at least one of said filaments being in series with said are electrodes and at least one other being in parallel therewith, and a resistance connected in series between one of said electrodes and its point of connection to said series circuit so as to lie in series with one of said filaments and in parallel with another.

2. An electric lamp comprising a pair of terminals, a plurality of resistances connected in series across said terminals and including at least one incandescent filament, a pair of arc electrodes connected to said series circuit at points of diffect of the resistances connected in series with ierent potential, at least one of said resistances being in series with said arc electrodes and at least one other resistance being in parallel with said electrodes and including means for heating the electrodes, and an additional resistance connected in series between one of said electrodes and its point of connection to said series circuit.

3. An electric lamp comprising a pair of terminals, resistance means within the lamp and permanently connected across said terminals, a pair of arc electrodes connected to said resistance means at points of different potential, the arc path between said electrodes being in parallel with one portion of said resistance means and in series with another portion, and an additional resistance connected in series between one of said electrodes and its point of connection to said resistance means, said last named resistance being of a material which becomes incandescent during normal operation of the arc.

4. An electric lamp comprising a pair of terminals, a bulb, means in said bulbproviding separate chambers therein, a plurality of filaments connected in series across said terminals, a pair of arc electrodes connected to said series circuit at points of different potential and enclosed in one of said chambers, at least one of said filaments being in series with said arc electrodes and enclosed in another of said chambers and at least one other filament being in parallel therewith, and a resistance connected in series between one of said electrodes and its point of connection to said series circuit.

5. An electric lamp comprising a pair of ter minals, a pluralityof resistances connected in series across said terminals and including at least one incandescent filament, a pair of arc electrodes connected to said series circuit at points of difierent potential, at least one of said resistances being in series with said are electrodes and at least one other being in parallel with said electrodes and including means for heating the electrodes, means dividing the interior of said lamp into separate chambers, said are electrodes and heating means being enclosed in one chamber, the resistance in series with the electrodes being enclosed in another chamber, and an additional resistance connected in series between one of said electrodes and its point of connection ..to said series circuit.

' 6. An electric lamp comprising a pair of terminals, a plurality of resistances connected in series across said terminals and including at least one incandescent filament, a pair of arc electrodes connected to said series circuit at points of different potential, at least one of said resistances being in series with said are electrodes and at least one other being in parallel with said electrodes and including means for heating the electrodes, and an additional resistance connected in series between one of said electrodes and its point of connection to said series circuit, said last named resistance constituting an incandescent filament.

7. An electric lamp comprising an outer bulb. a closed inner bulb, a pair of lamp terminals, an incandescent filament in said outer bulb, a pair of arc electrodes in said inner bulb, means for heating said electrodes, said filament and heating means being connected in series across the lamp terminals and said are electrodes being connected to opposite ends of said heating means,

and a resistance interposed between one of said electrodes and its point of connection to said heating means. v

8. An electric lamp comprising a bulb, a pair of lamp terminals, resistance means permanently connected across said terminals in a series circuit and comprising a pair of heating filaments and an incandescent filament connected in series therebetween, a pair of arc electrodes adapted to be heated by said heating filaments, connections from each arc electrode to said series circuit, and a resistance interposed in one of said connections.

9. An electric lamp comprising a bulb, a pair of lamp terminals, resistance means permanently connectedacross said terminals in a series circuit and comprising a pair of heating filaments and an incandescent filament connected in series therebetween, a pair of arc electrodes adapted to be heated by said heating filaments, means in said lamp providing separate chambers, said incandescent filament being disposed in one of said chambers and said are electrodes in another chamber, connections from each arc electrode to said series circuit, and a resistance interposed in one of said connections.

GEORGE SPERTI. 

